Method of hermetically sealing electrical conductors through or into hard vitreous substances.



G. B. BURNSIDB. METHOD OF HERMETIUALLY SEALING ELEOTRIGAL OONDUGTORSTHROUGH OR'INTO HARD VITREOUS SUBSTANCES.

' APPLIOATIOH FILED APILZQ, 1911. 1 ,01 6,320.

Patented Feb.6,1912

' trical conductor.

UNITED STATES PATENT onnicn.

GEORGE BARNHILL BURNSIDE, OF RENFBEW, SCOTLAND.

METHOD OF HERMETICAIILY SEALING ELECTRICAL CONDUCTOBS THROUGH OB INTOHARD VITREOUS SUBSTANCES.

Specification of Letters Patent.

Application fled April 29, 1911.

Patented Feb. 6, 1912.

Serial No. 624,284.

To all whom it may concern:

Be it known that I, GEORGE BARNHILL BUBNSIDE, a subject of the King ofGreat Britain, residing at Renfrew, Scotland, have invented a certainnew and useful Imroved Method of Hermetically Sealing lectricalConductors Through or into Hard Vitreous Substances, of which thefollowing is a specification.

This invention relates to an improved method of hermetically sealingwires, or other electrical conductors, through or into lead glass, Jenaglass, quartz glass or other vitreous substance.

Hitherto in connection with the manufacture of incandescent electriclam'ps, mercury or other vapor apparatus and .other kinds of vacuumtubes, it has been the custom to employ flux glass around the conductors of copper or short pieces of platinum wire, or wires of specialshape in some cases flattened and in other cases having enlargedportions, advantage being taken of t e contraction and expansion of thewire. Solutions of india-rubber and copal cement have also been employedor the thermal expansions of the glass and the electrical conductor hasto be guarded against.

My invention consists in first heating the vitreous substance whichsurrounds the electrical conductor and with it forms the seal, untilperfect cohesion has been efiected between the vitreous substance andthe conductor, and then allowingthe vitreous subtance to col to about adull red heat, whereafter the seal is suddenly cooled or put through arocess of hardening, the vitreous substance ing thus fixed around theelec- It is desirable to allow such a quantity of vitreous substancearound the electrical conductor as is consistent with mechanicalstrength. By employing this method a gas pressure tight joint orhermetic seal can be made between the wire, or other electricalconductor and the vitreous substance, without any difliculty. arisingconditions experienced during or after the actual working of theelectric lam or tube.

In order that the invention may e clearly understood I will nowdescribe, by way of example, the application of the invention inconnection with the sealing of electrical conductors throughthe-vitreous substance of incandescent electric lamps, vapor electricapparatus olxother forms of vacuum tubes.

The electrical conductor is placed through or into an aperture orpassage in the vitreous substance.- This aperture should be just largeenough to admit the conductor so that oxidation may be prevented as faras possible, when the conductor is heated. The vitreous substancesurrounding the electrical conductor is then strongly heated by means ofa small blow pipe flame until perfect cohesion has been attained betweenthe vitreous substance and the electrical con-" and hardened; Thiscooling or hardening process lasts about thirty seconds. In practice ithas been found very convenient to fix the vitreous substance in itsstate of cohesion around the electrical conductor by bringing a smallvessel of oilup around the sealor joint and applying it in the mannerabove described.

The electrical conductor should be per f tl clean and smooth and it mayif desired: be coated to prevent the oxidat1on,be fore it sealed throughor into the vitreous substance.

If the conductor is required to carry an electrical current of not morethan about fifteen amperes it is convenient to have the conductor in theform of a solid wire of circular cross section. If the current to becarried by the electrical conductor exceeds fifteen am res the conductormay very conveniently b e tubular, referably of circular ductingsubstance. The tubular form of conductor is used in this case because itcan be more eflectively cooled throughout by the cooling mediumv bothoutside and inside it than would be the case with a solid conductor ofthe same area of cross section.

Referring to the accompanying drawingsz-Figure 1 shows a seal for Jenaglass combustion tubing. Fig. 2 shows a seal A for lead or German glass.Fig. 3 is an enlarged view showing the seals A,'A, suitable forincandescent lamps. Figs. 4 and 5. show seals A, A, for a tubularelectrical conductor B suitable in cases where a large electricalcurrent is required. In Fig. 5 the electrical conductor B is shownclosed at one end. This form is especially useful when applied tothecase of mercury vapor lamps or rectifiers the tubular shell beingmade of a substance which does not form an amalgam and thus forming aprotecting cover to a highly conducting material such as copper, whichis acted on by mercury. The electrical conductor B is sealed in thesealA which latter is cooled and thereby I hardened in the. coolingmedium by gradually increasing immersions until the part indicated bythe dotted line, at G, is reached.

F igs..1 and 2, show suitable proportions for the conductor B and theseal A for combustion tubing and the like, while Fig. 3 shows aconvenient arrangement for adapting the seal to the central stem of anincandescent electric lamp.

D represents an extension to .suit metallic filament electric lamps.

E is the plug of conducting material for the tubular form of conductor.

A very effective seal can be obtained by the herein described methodbetween a solid copper wire conductor up to 1.23 millimeters in diameterand German glass. Platinum wires, varying in thickness up to 1 millimeter have been successfully sealed in Jena glass and other vitreoussubstances. I have also sealed thicker wires very effectively. In thecase of tubular conductors there is practically no limit to themagnitude of the cross-sectional area of the conductors.

Having now fully described my invention what I claim and desire tosecure by Letters Patent is v 1. A method of hermetically sealingelectrical conductors through or into vitreous substances which consistsin first heating the vitreous substance, which surrounds the electricalconductor and with it forms the seal, until perfect cohesion has beeneffected between the vitreous substance and the conductor and thenallowing the vitreous substance to cool to about a dull red heatwhereafter the seal is suddenly cooled or put through a process ofhardening, the vitreous substance being thus fixed around the electricalconductor.

2. A method of hermetically sealing electrical conductors through orinto vitreous substances which consists in first heating the vitreoussubstance, which surrounds the electrical conductor and with it formsthe seal, until perfect cohesion has been eifected between the vitreoussubstance and the conductor and then allowing the vitreous substance tocool to about a dull red heat, whereafter the seal is suddenly cooledorput through a process of hardening by immersing it into an oleaginoussubstance the vitreous substance being thusfixed around the electricalconductor.

In testimony whereofrI afiix my signature in presence of two witnesses.

GEORGE mammal. BURNSIDE.

Witnesses:

WILLIAM CARRUTHERS, H. D. FITZPATRICK.

